play it down

Play it down--keep things quiet and calm 保持低調

play it up: being excited, having energy. 瘋狂地玩，高調地玩

for example, in a surprise party,everybody is quiet waiting for the main role such as the birthday girl or boy, once they show up people play it up.

Let us play it up this Saturday, let all people know that we have a party, let them show up.